The subject invention relates to methods of controlling dispensing systems having a robot for application of a material to a workpiece. Specifically, the methods of controlling the dispensing systems prevent any gaps, overlaps, or puddles in the material on the workpiece.
Many industries apply a material to a workpiece during manufacturing to accommodate a multitude of processes. For example, manufacturers may apply the material to a workpiece to prevent any moisture or contaminants from entering a cavity formed when combining two or more workpieces. The material is typically applied by a conventional dispensing system that includes a specialized robot. The robot applies the material to a workpiece as the robot moves along a motion segment at an operational speed. Application of the material to the workpiece is automated, and manufacturer specifications governing the application of materials allow few, if any, gaps, overlaps, or puddles in the material on the workpiece. A gap in the material creates such problems as the intrusion of moisture or contaminants into the cavity formed when combining two or more workpieces. Overlaps or puddles in the material causes an uneven fit between the workpieces.
When an error occurs in the dispensing system, the gaps, overlaps, and puddles in the material occur. Current dispensing systems have the ability to detect when the error has occurred as the robot moves along a motion segment at an operational speed. The dispensing systems of the prior art are programmed to discontinue dispensing a first portion of the material when the error is detected. An operator may also discontinue dispensing a first portion of the material manually. Regardless of how dispensing is discontinued, the robot decelerates from the operational speed to a rest position after the dispensing is discontinued. The rest position is generally beyond the position along the motion segment at which the application of the first portion of the material ended. Therefore, if dispensing resumes from the rest position, a gap occurs in the material on the workpiece.
Current dispensing systems overcome this problem by determining a backup distance, by relocating the robot to a backup position along the motion segment based on the backup distance, and by setting a time to resume dispensing. These steps are performed to ensure that the robot applies a second portion of the material at a reapplication position that is at or near where the application of the first portion of the material ended, and also to ensure that the robot reaches the operational speed at least by the time the robot reaches the re-application position. Otherwise, a gap or overlap in the material on the workpiece occurs. Additionally, a puddle of the material on the workpiece may occur if the robot has not reached the operational speed. Further, if the robot is improperly relocated to the backup position, or if the time to resume dispensing is improperly set, the gap, overlap, or puddle in the material also occurs.
The disadvantage of the prior art is the method in which the dispensing system is controlled to prevent the gaps and overlaps in the material on the workpiece. The backup distance and time to resume dispensing are not based on the operational speed of the robot in the prior art methods. As such, the backup distance and time to resume dispensing must be adjusted by trial and error for each operational speed of the robot. Otherwise, there is no reasonable assurance that the re-application position will be at or near where the application of the first portion of the material ended or that the operational speed of the robot will be reached at least by a time that the robot reaches the re-application position. In view of the fact that the method of the prior art can not be used for different operational speeds of the robot, the prior art method realizes high costs associated with adjusting the backup distance and time to resume dispensing for each operational speed. Additionally, the robot used in the prior art methods is limited to only one application.
As a result, it is desirable to develop a method that automatically determines the backup distance based on the operational speed of the robot thereby eliminating the requirement of setting the time to resume dispensing. Determining the backup distance based on the operational speed prevents any gaps or overlaps from occurring in the material during the application of the material to the workpiece.
A method of controlling a dispensing system is disclosed. The dispensing system includes a robot for application of a material to a workpiece. The method of controlling the dispensing system according to the subject invention prevents any gaps or overlaps in the material on the workpiece. The method of the subject invention also prevents any puddles of the material on the workpiece. The method includes the step of moving the robot along a motion segment at an operational speed between a first position and a second position. As the robot moves, a first portion of the material is applied to the workpiece. The application of the first portion of the material is discontinued in response to an error that occurs during the application of the first portion. A re-application position for the material, indicating where the robot begins applying a second portion of the material, is established along the motion segment in response to the error. The method of the subject invention continues by determining a backup distance indicating where the robot is to be relocated relative to the re-application position. The backup distance is based on the operational speed of the robot to ensure that the robot reaches the operational speed at least by a time that the robot reaches the re-application position. The method of the subject invention then continues by relocating the robot to a backup position based on the determined backup distance.
The subject invention also provides a method for controlling a dispensing system that includes the steps above, but further includes establishing a tracking position for the robot along the motion segment. The tracking position is established in response to the error that occurs during the application of the first portion. The tracking position relates to the re-application position and is used to establish the re-application position. The method continues by monitoring the tracking position as the robot moves from the backup position toward the reapplication position to instruct the robot to begin application of a second portion of the material to the workpiece at the re-application position. As such gaps, overlaps, and puddles in the material on the workpiece are prevented.
An intelligent error-recovery method is also disclosed. The method is for controlling a system including the robot to ensure that an operational parameter is achieved after the error occurs in the system. The robot moves along an operating path between the first position and the second position and performs an operation as the robot moves. The operation being performed requires the operational parameter to ensure that the operation is completed. The operation being performed with the robot is discontinued in response to the error, and a transitional position is established when the error occurs. The transitional position indicates a location of the robot along the operating path when the error occurs. The robot is relocated to a restart position after the error occurs and the robot moves from the restart position toward the second position. The intelligent error-recovery method of the subject invention verifies that the operational parameter is achieved at least by a time the transitional position is reached by the robot to ensure that the operation is completed by the robot.
The advantage of the subject invention over the prior art is the method in which the robot is controlled to prevent any gaps, overlaps, or puddles in the material on the workpiece. In the prior art, the backup distance and time to resume dispensing are variables that must be adjusted by trial and error for each operational speed of the robot. On the other hand, the method of the subject invention automatically determines the backup distance based on the operational speed of the robot to ensure that the re-application position is at or near where the application of the first portion of the material ended and also to ensure that the operational speed of the robot is reached at least by a time that the robot reaches the re-application position. As such, the method of the subject invention is able to be used across many different applications that utilize various operational speeds of the robot to prevent any gaps, overlaps, or puddles in the material on the workpiece.